title: How reliable are lower-limb kinematics and kinetics during a drop vertical jump?
abstract: OBJECTIVE
  As drop vertical jumps (DVJ) are widely used as a screening task, the assessment of the reliability of lower-limb biomechanical parameters during DVJ is important. The aim of this study was to assess the reliability of the kinematic and kinetic peak values as well as of the waveforms for lower-limb parameters obtained with the Liverpool John Moores University biomechanical model (LJMU model) during performance of DVJ.
  
  
  METHODS
  The reliability was analyzed by calculating the intertrial (o(trial)), intersession (o(sess)), and intertherapist (o(ther)) errors of hip and knee joint parameters in a repeated-measures design including two therapists and a total of six sessions.
  
  
  RESULTS
  The results showed o(trial) that ranged from 1.1° to 3.5° for all peak kinematic parameters and from 3.6 to 12.9 N · m for all peak kinetic parameters. The o of the peak values ranged from 1.9° to 5.7° for all angles and from 5.4 to 19.8 N · m for the hip and knee joint moments in all planes. The o(sess) of the peak values ranged from 2.7° to 6.4° for all angles and from 5.8 to 22.4 N · m for all moments. Most of the kinematic and kinetic peak parameters had o(ther-trial) ≤ 2.0° and 4.3 N · m, respectively, suggesting a small extrinsic variability. Furthermore, the entire waveforms also showed a rather high o(trial) relative to other types of variability.
  
  
  CONCLUSIONS
  The present findings indicated that DVJ kinetics and kinematics show small extrinsic variability. The reported errors are useful for clinical interpretation processes of DVJ performance as screening task for injury risk and rehabilitation outcome taking into consideration the different types of measurement error over time.
authors.affiliation: 1Musculoskeletal Rehabilitation Research Group, Faculty of Kinesiology and Rehabilitation Sciences, Department of Rehabilitation Sciences and Physiotherapy, KU Leuven, Leuven, BELGIUM; and 2Research Institute for Sport and Exercise Sciences, Faculty of Science, Liverpool John Moores University, Liverpool, UNITED KINGDOM.
authors.forename: Bart
authors.initials: B
authors.lastname: Malfait
authors.forename: Sean
authors.initials: S
authors.lastname: Sankey
authors.forename: Raja M
authors.initials: RM
authors.lastname: Firhad Raja Azidin
authors.forename: Kevin
authors.initials: K
authors.lastname: Deschamps
authors.forename: Jos
authors.initials: J
authors.lastname: Vanrenterghem
authors.forename: Mark A
authors.initials: MA
authors.lastname: Robinson
authors.forename: Filip
authors.initials: F
authors.lastname: Staes
authors.forename: Sabine
authors.initials: S
authors.lastname: Verschueren
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D059385:Plyometric Exercise; D015203:Reproducibility of Results; D055815:Young Adult